The main structural components of the drive train in a typical wind turbine are a rotor hub, a main shaft and a gearbox that is connected to the generator by a high-speed shaft. The gearbox housing is connected to the main frame of the wind turbine. The primary purpose of these structural components is to transfer the driving torque generated by the rotor to the generator and increase the shaft speed in order to achieve a suitable rotational speed of the generator rotor. A secondary purpose is to transfer the weight of the rotor, the thrust and the asymmetrical rotor moments, i.e. tilting and yawing moments, to the main frame and thereby further to the tower and the foundation.
In land-based wind turbines, the component integration has been an important driver for their design, understanding component integration as a way to reduce the weight of the drive train and to avoid mutual interference of the external and internal loads on the different components.
An approach in this respect regarding gearboxes can be found in EP 2 072 858 that discloses a compact gearbox design having the planet carrier of the first stage connected directly to the main shaft, without bearings to support it. The gearbox assembles a flexible planet carrier system to avoid an eccentricity of the planet carrier with respect to the ring gear caused by deformations of the main shaft.
The component integration is also a driver for the design of off-shore wind turbines and particularly for their gearboxes but the above-mentioned approach is not appropriate for them because of the larger dimensions they usually have.
There is therefore a need for integrated gearboxes for large wind turbines, particularly off-shore wind turbines
The present invention is intended to satisfy said demand.